CNN — (CNN) -- Flights are canceled, cars are piling up in icy crashes, and millions are stranded -- many at home, others along roads. And this isn't just typical winter fare slamming the Northeast. It's part of a rare pattern walloping virtually the entire United States at once.
"It's very unusual," CNN meteorologist Dave Hennen said Monday. "This literally spreads across the entire U.S., and we're 12 days from the official start of winter."
Temperatures have plunged below freezing in parts of California and Nevada, including Las Vegas. Wind chills are 40 below zero in the Midwest. Snow and ice have blanketed a large swath of the Northeast, all the way up to Maine.
It was warmer in Anchorage, Alaska, on Monday morning than it was in St. Louis and Denver.
In New York City, the temperature with wind chill was 25 degrees Monday morning. But that was balmy compared to Bismarck, North Dakota, at 29 below zero.
Across the country, most temperatures are between 10 and 20 degrees below average.
And some places are receiving record snowfall. Philadelphia broke its daily record Sunday, with more than 8 inches.
In Washington, federal agencies opened two hours late Monday due to the weather.
In the Dallas-Fort Worth area, about 20,000 customers were without power Monday, according to power company Oncor.
More than 2,600 flights were canceled nationwide Sunday, and about 1,500 have been nixed Monday, according to the website Flightaware.com. Hundreds of flights were canceled in and out of Dallas due to freezing fog.
Dangerous travel conditions
At least seven people have died in storm-related incidents in Texas, Arkansas and New Mexico since Thursday, officials said. Most were involved in traffic crashes.
In Arizona, a Saturday night snowstorm stranded 300 vehicles along Interstate 15. Rigs jackknifed and passenger cars slid into rigs, causing chain-reaction crashes and an enormous backup, Arizona Department of Public Safety Officer Bart Graves said. Authorities shut the interstate for more than 12 hours to clear the road.
"We had travelers running out of gas. They provided them food, water, and blankets," Graves said.
Some residents in the Dallas suburb of Plano had to deal with an unusual danger: sheets of ice cascading from buildings to the sidewalks and streets.
"The apocalypse has started," one man said shortly before layers of ice fell onto cars.
Late Sunday night in New York, there was a 20-car pileup on the Bronx River Parkway. Forty people were injured, none seriously, authorities said.
Freezing rain is expected to fall from central Virginia to southeast New York on Monday. Some parts could see up to 1/4 inch of ice.
Stillness, frustration, and beauty
"My wife, 8-year-old daughter, and I had started to head to a holiday party about 11:30 yesterday morning, but after 2 1/2 hours of trying to drive in the snow, we turned around and headed back home," said Mark Schroy of New Castle, Delaware.
When they got back to their house, they had to shovel out the driveway all over again from the inches of snow that had poured down in the meantime.
Schroy shared a panoramic photo of the snow with CNN iReport.
Jeffrey Beer photographed the icy aftermath of the storm in Fairfield Bay, Arkansas. "Ice pellets were 'raining' down, stinging my eyes and any exposed skin," he said.
"For me, the highlight is how beautiful everything looks. It contrasts strongly with how it feels, and how it restricts activities. ... I'm still housebound, as are most of the people that live along side streets in this region."
In Eugene, Oregon, Steve Gladfelter photographed the wintry conditions that accompanied subzero temperatures over the weekend. He's never seen anything like it in the town where he's lived for 17 years.
"This weather is not at all typical for this area at this time of year, or at any other time of year. Snow is rare, and extended deep freezes are very rare," he said.
Stranded in airports
Canadian James Archibald has spent four days living at Dallas/Fort Worth International Airport in the bizarre deep freeze.
"I just don't understand why they can't get the ice off the runway," he said. "I know it's for our own safety, but it's getting a bit silly."
About 650 passengers spent Sunday night at DFW airport -- fewer than the previous night, the airport said.
-- CNN's Indra Petersons, Judson Jones, Ed Lavandera, Dave Alsup and Emily Minner contributed to this report.